Port of internal combustion engine

ABSTRACT

A port that communicates an inside of a combustion chamber of an internal combustion engine with an outside of the combustion chamber includes a throat portion that has at least a portion of a truncated cone shape, a valve seat portion that is connected to one end portion of the throat portion to communicate the throat portion with the inside of the combustion chamber, and a passage portion that is connected to the other end portion of the throat portion to communicate the throat portion with the outside of the combustion chamber.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-121179 filed on May 31, 2011 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a port of an internal combustion engine.

2. Description of Related Art

A combustion chamber of an internal combustion engine is typically communicated with the outside of the combustion chamber by an intake port so that gas that has not yet been combusted (such as air, an air-fuel mixture, or the like) can be introduced into the combustion chamber, as well as communicated with the outside of the combustion chamber by an exhaust port such that combusted gas (i.e., exhaust gas) can be discharged outside of the combustion chamber. The modes in which these gases are introduced and discharged may have a variety of effects on the characteristics of the internal combustion engine, as is well known. Among these modes, a related intake port that is able to smoothly introduce gas into the combustion chamber and that enables a rotating flow (such as tumble) caused by the introduced gas to be created inside the combustion chamber has been proposed.

For example, one such related intake port (hereinafter, also referred to as “related port”) includes a throat portion, a valve seat portion that is connected to one end of the throat portion, and a passage portion that is connected to the other end of the throat portion. The valve seat portion of the related port has a plurality of annular surfaces. In this related port, the plurality of annular surfaces form a virtual curved surface, and the curvature radius of this curved surface differs depending on the position in the circumferential direction of the port. With this related port, the amount of gas introduced into the combustion chamber is increased, and the degree of rotating flow (i.e., tumble) created inside the combustion chamber is increased, by appropriately setting the curvature radius of this curved surface according to the position (see Japanese Patent Application Publication No. 2009-57830 (JP 2009-57830 A), for example). In this way, from the past it has been desirable to appropriately control the flow of gas in the combustion chamber.

The port of an internal combustion engine is typically formed by separately forming each of the portions (such as the throat portion, the valve seat portion, and the passage portion of the related port) that make up the port in order. For example, in a related port, first a predetermined member (such as a cylinder head) is cast to form the passage portion. Next, the cast member is machined to form the throat portion in the end portion of the passage portion. Then the cast member is further machined to form the valve seat portion on the end portion of the throat portion. It is through these processes that the related port in which the valve seat portion, the throat portion, and the passage portion are connected is formed.

However, there may be manufacturing variation among the portions that make up the port (i.e., differences in dimension and the like among the same type of part that may occur during manufacture; hereinafter, simply referred to as “variation”), as is well known. When the degree of variation is small, the effect of this variation on the characteristics of the port is negligible from the viewpoint of appropriately controlling the flow of gas in the combustion chamber. In contrast, when the degree of variation is fairly large, the intended characteristics of the port are unable to be sufficiently obtained, so the flow of gas in the combustion chamber may not be able to be appropriately controlled.

SUMMARY OF THE INVENTION

The invention thus provides a port of an internal combustion engine in which the intended characteristics of the port are able to be obtained, even if there is variation among various portions that make up the port of the internal combustion engine.

One aspect of the invention relates to a port that communicates an inside of a combustion chamber of an internal combustion engine with an outside of the combustion chamber. This port includes a throat portion that has at least a portion of a truncated cone shape, a valve seat portion that is connected to one end portion of the throat portion to communicate the throat portion with the inside of the combustion chamber, and a passage portion that is connected to the other end portion of the throat portion to communicate the throat portion with the outside of the combustion chamber.

The port may be provided between an intake passage (e.g., an intake manifold) of the internal combustion engine and the combustion chamber, or between an exhaust passage (e.g., an exhaust manifold) of the internal combustion engine and the combustion chamber. Further, for example, the port may be provided, as part of the intake passage, on an end portion of the intake passage where the intake passage is connected to the combustion chamber, or as part of the exhaust passage, on an end portion of the exhaust passage where the exhaust passage is connected to the combustion chamber. That is, the port may be a part of the intake passage or the exhaust passage, or may be a portion that is different from the intake passage and the exhaust passage.

In other words, the port may form part of a flow path through which flows gas (e.g., air or an air-fuel mixture of air and fuel) that is introduced from outside of the combustion chamber into the combustion chamber, or gas (e.g., exhaust gas) that is discharged from inside of the combustion chamber to outside of the combustion chamber. More specifically, the port may be the flow path itself (i.e., a space or a cavity) through which these gases pass, or a member that defines this flow path (i.e., the space or cavity).

As can be understood from the description above, the outer peripheral surface of the flow path itself through which gas passes (i.e., a virtual surface that defines the space of the flow path) and an inner peripheral surface of the member that defines this flow path (i.e., an inner peripheral wall surface that defines the space formed inside of the member for providing the flow path) have shapes that correspond with each other, and contact each another. Therefore, in terms of considering the shape of the port, these may match. Therefore, hereinafter, regarding the port, the outer peripheral surface of the flow path itself through which gas passes and the inner peripheral surface of the member that defines this flow path may each also simply be referred to as a “peripheral surface of the port”. Moreover, regarding the throat portion, the valve seat portion, and the passage portion as well (the details of these portions will be described later), similarly, the outer peripheral surface of the flow path itself through which gas passes and the inner peripheral surface of the member that defines this flow path may also simply be referred to as a “peripheral surface of the throat portion”, a “peripheral surface of the valve seat portion”, and a “peripheral surface of the passage portion”.

The throat portion has at least a portion of a truncated cone shape. In other words, the space that forms the throat portion may be a space of at least a portion of the space of the truncated cone shape. The throat portion is a portion that exists between a valve seat portion and a passage portion that will be described later, and is where these two portions are connected.

As described above, the port may be the flow path itself or a member that defines the flow path. Therefore, in this aspect, the expression “the throat portion is a truncated cone shape” may refer to (a) the portion itself (i.e., the space or cavity) that is referred to as the throat portion of the flow path being a truncated cone shape, or (b) a member that defines the portion (i.e., the space or cavity) that is referred to as the throat portion of the flow path being formed such that this portion is a truncated cone shape.

Further, in this aspect, the expression “the throat portion is at least a portion of the truncated cone shape” may refer to (c) the throat portion being a complete truncated cone shape (i.e., three dimensional surrounded by a round bottom surface and upper surface, and a band-shaped side surface, or (d) the throat portion being a shape obtained by removing a portion from a complete truncated cone (see FIG. 3, for example).

The expression “the throat portion has at least a portion of a truncated cone shape” may refer to the throat portion including a shape understood from (a) to (d) described above (i.e., part or all of the throat portion being a truncated cone shape). Thus, for example, the throat portion may be a shape obtained by a combination of a truncated cone shape and another shape.

The valve seat portion is connected to one end portion of the throat portion so as to communicate the throat portion with the inside of the combustion chamber. In other words, the valve seat portion is provided on a portion of the port that faces the inside of the combustion chamber. The valve seat may be a flow path itself or a member that defines a flow path, just as described above. As is well known, the amount of gas that passes through the port is able to be adjusted by having a predetermined member (such as a valve) come into contact with or move away from the valve seat portion.

The shape of the valve seat portion is not particularly limited. The details of the shape of the valve seat portion will be described later.

The passage portion is connected to the other end portion of the throat portion so as to communicate the throat portion with the outside of the combustion chamber. The passage portion may be a flow path itself or a member that defines a flow path, just as described above.

The shape of the passage portion is not particularly limited. For example, a portion having at least a portion of a round columnar shape, or a portion having at least a portion of a square columnar shape or the like may be used as the passage portion. In other words, a passage portion formed by a space of at least a portion of a space of a round columnar shape, or a passage portion formed by a space of at least a portion of a space of a square columnar shape or the like may be used as the passage portion.

Hereinafter, the position where the throat portion is connected to the valve seat portion may also be referred to as a “connecting position of the throat portion and the valve seat portion”, and the position where the throat portion is connected to the passage portion may also be referred to as a “connecting position of the throat portion and the passage portion”.

In the port of this aspect structured as described above, the flow direction of the gas that passes through the port may change at the connecting position of the throat portion and the valve seat portion, and at the connecting position of the throat portion and the passage portion. For example, when the peripheral surface of the passage portion is inclined at a specific angle (hereinafter, also referred to as a “connecting angle”) with respect to the peripheral surface of the throat portion at the connecting position of the throat portion and the passage portion, when gas passes by the connecting position, the flow direction of the gas that flows close to these peripheral surfaces may change according to the connecting angle (i.e., so as to follow the peripheral surface of the throat portion and the peripheral surface of the passage portion).

Therefore, in order to appropriately control the flow of gas inside the combustion chamber, it is desirable that the connecting angle change as little as possible even if there is variation among the members that make up the port (i.e., the throat portion, the valve seat portion, and the passage portion).

However, if the throat portion has a semispherical shape (i.e., a shape that differs from the truncated cone shape of this aspect), for example, and the passage portion is connected to a portion of a spherical surface of this semispherical shape, the connecting angle of the throat portion and the passage portion may differ depending on the connecting position of the throat portion and the passage portion. This is because the connecting angle of the throat portion and the passage portion corresponds to an angle that is defined by the peripheral surface of the passage portion and the tangential plane of the hemisphere at the connecting position (i.e., an angle formed between the peripheral surface of the passage portion and the tangential plane of the hemisphere at the connecting position), and the slope of the tangential plane of the hemisphere typically differs depending on the connecting position. Therefore, in this case, if there is variation among the members that make up the port, this variation may cause the connecting position of the throat portion and the passage portion to change, which in turn may cause the connecting angle to change (see FIG. 4, for example).

On the other hand, the throat portion of the port of this aspect has at least a portion of a truncated cane shape. Therefore, if the passage portion is connected to a portion of the side surface of the truncated cone shape, the connecting angle of the throat portion and the passage portion is able to be the same (constant) regardless of the connecting position of the throat portion and the passage portion. This is because the connecting angle of the throat portion and the passage portion corresponds to an angle that is defined by the peripheral surface of the passage portion and the side surface of the truncated cone at the connecting position (i.e., an angle formed between the peripheral surface of the passage portion and the side surface of the truncated cone at the connecting position), and the slope of the side surface of the truncated cone is the same, even if the connecting position is different, as long as the connecting position is on the same line of the truncated cone. Accordingly, in the port of this aspect, even if there is variation among the members that make up the port, the connecting angle will not change as long as the connecting position of the throat portion and the passage portion changes on the same line due to the variation. Further, with the port of this aspect, if the connecting position of the throat portion and the passage portion does not change on the same line, or even if the slope of the peripheral surface of the passage portion changes, typically the connecting angle is able to be inhibited from changing compared with the throat portion that has a semispherical shape described above.

Furthermore, with the port of this aspect, even if the passage portion is connected to a portion of an upper surface or a bottom surface of the truncated cone shape of the throat portion, the upper surface or the side surface of the truncated cone shape of the throat portion is a flat surface, so the connecting angle is able to be inhibited from changing when there is variation among the members that make up the port, compared with a throat portion that has a semispherical shape.

In addition, as can be understood from the description above, regarding the connecting angle of the throat portion and the valve seat portion as well, this connecting angle can be inhibited from changing even if there is variation among the members that make up the port, just as described above.

The expression the “passage portion is connected to a portion of a side surface of the truncated cone shape of the throat portion” may also be expressed as “at least a portion of a boundary line between the throat portion and the passage portion is on a side surface of the truncated cone shape of the throat portion.”

In this way, the port of this aspect is formed such that variation among the members (i.e., the throat portion, the valve seat portion, and the passage portion) that make up the port affects the characteristics of the port as little as possible (e.g., such that the connecting angle is maintained at an angle in a range within which the intended characteristics of the port can be obtained). Therefore, with the port of this aspect, the intended characteristics of the port are able to be obtained to the greatest extent possible, even if there is variation among the members that make up the port.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic diagram of an internal combustion engine to which a port according to a first embodiment of the invention may be applied;

FIG. 2 is a view schematically showing a cross section of the port according to the first embodiment of the invention;

FIG. 3 is an enlarged perspective view schematically showing the port according to the first embodiment of the invention;

FIG. 4 is a schematic diagram of the manner in which gas passes through a port according to related art;

FIG. 5 is a schematic diagram of the manner in which gas passes through the port according to the first embodiment of the invention;

FIG. 6 is an enlarged perspective view schematically showing a port according to a second embodiment of the invention;

FIG. 7 is a view schematically showing a cross section of the port according to the second embodiment of the invention;

FIG. 8 is a view schematically showing a cross section of a port according to a third embodiment of the invention;

FIG. 9 is an enlarged perspective view schematically showing a port according to a fourth embodiment of the invention;

FIG. 10 is a view schematically showing a cross section of a port according to related art;

FIG. 11 is a schematic diagram of the flow, inside of a combustion chamber, of gas that has passed through the port according to the related art;

FIG. 12 is another schematic diagram of the flow, inside of a combustion chamber, of gas that has passed through the port according to the related art;

FIG. 13 is a schematic diagram of the flow, inside of a combustion chamber, of gas that has passed through the port according to the fourth embodiment of the invention; and

FIG. 14 is a graph showing a simple view of the relationship between tumble ratio and flow coefficient.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments (i.e., first to fourth embodiments) of a port of an internal combustion engine according to the invention will be described with reference to the accompanying drawings.

First Embodiment Outline of the Port

FIG. 1 is a view schematically showing the structure of a system in which ports (i.e., an intake port and an exhaust port) according to a first embodiment of the invention have been applied to an internal combustion engine 10. The internal combustion engine 10 is a four-cycle spark-ignition multiple cylinder (four cylinder) engine. FIG. 1 is a view of only the cross section of one of the plurality of cylinders. The other cylinders have the same structure as this cylinder.

This internal combustion engine 10 includes a cylinder block portion 20, a cylinder head portion 30 that is fixed to an upper portion of the cylinder block portion 20, an intake system 40 for introducing gas that is a mixture of air and fuel (i.e., an air-fuel mixture) into the cylinder block portion 20, an exhaust system 50 for discharging gas (i.e., exhaust gas) from the cylinder block portion 20 to outside of the internal combustion engine 10, an accelerator pedal 61, various sensors 71 to 78, and an electronic control unit (ECU) 80.

The cylinder block portion 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 moves in a reciprocating manner inside the cylinder 21. This reciprocating movement of the piston 22 is transmitted to the crankshaft 24 via the connecting rod 23, causing the crankshaft 24 to rotate. A combustion chamber 25 is defined by an inner peripheral surface of the cylinder 21, an upper surface of the piston 22, and a lower surface of the cylinder head portion 30.

The cylinder head portion 30 includes an intake port 31 that is communicated with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft 33 that drives the intake valve 32, an injector 34 that injects fuel into the intake port 31, an exhaust port 35 that is communicated with the combustion chamber 25, an exhaust valve 36 that opens and closes the exhaust port 35, an exhaust camshaft 37 that drives the exhaust valve 36, a spark plug 38, and an igniter 39 that includes an ignition coil that generates high voltage that is applied to the spark plug 38.

FIG. 2 is a view schematically showing a cross section of the combustion chamber 25, the intake port 31, and the exhaust port 35 when a region including the combustion chamber 25, the intake port 31, and the exhaust port 35 has been cut along a plane parallel to the axis of the combustion chamber 25. To facilitate understanding, members (such as the spark plug 38) that are not absolutely necessary to describe the structure of the port according to this embodiment are not shown in FIG. 2.

Hereinafter, of the ports according to the first embodiment, the intake port 31 will be described in more detail. As shown in FIG. 2, the intake port 31 includes a valve seat portion 31 a, a throat portion 31 b, and a passage portion 31 c.

In this embodiment, the intake port 31 represents a flow path itself, through which an air-fuel mixture flows, that is between the combustion chamber 25 and an intake manifold 41 that will be described later, or a member that defines this flow path.

The valve seat portion 31 a is connected to one end portion of the throat portion 31 b (i.e., the end portion closer to the combustion chamber 25 than the other end portion that will be described later; hereinafter this one end portion will be referred to as a “combustion chamber side end portion”) so as to communicate the throat portion 31 b with the inside of the combustion chamber 25. Meanwhile, the passage portion 31 c is connected to the other end portion of the throat portion 31 b (i.e., the end portion that is closer to the intake system 40 than the one end portion described above; hereinafter this other end portion will be referred to as an “intake side end portion”) so as to communicate the throat portion 31 b with the outside of the combustion chamber 25. The throat portion 31 b is located between the valve seat portion 31 a and the passage portion 31 c, and is connected to both the valve seat portion 31 a and the passage portion 31 c.

FIG. 3 is an enlarged perspective view schematically showing the intake port 31. As shown in FIG. 3, the throat portion 31 b has a portion of a truncated cone shape (hereinafter, simply referred to as a “truncated cone portion”) 31 b 1, and a portion 31 b 2 of another shape (a round columnar shape in this embodiment). The truncated conical portion 31 b 1 has a shape that can be obtained by removing a portion (i.e., a region 31 b 3 indicated by the broken line) from a complete truncated cone, as shown by the hatched portion. In this way, the throat portion 31 b has at least a portion of a truncated cone shape.

In this embodiment, the throat portion 31 b having at least a portion of a truncated cone shape represents to a portion referred to as the throat portion of the flow path through which the air-fuel mixture flows having at least a portion of a truncated cone shape, or a member that defines the portion being formed such that the portion has at least a portion of a truncated cone shape.

The passage portion 31 c is connected to a portion of a side surface of the truncated cone shape (i.e., the truncated cone portion) 31 b 1 of the throat portion 31 b. In other words, at least a portion (all in this embodiment) of a boundary line between the throat portion 31 b and the passage portion 31 c is on a side surface of the truncated cone shape 31 b 1 of the throat portion 31 b. The passage portion 31 c has a round columnar shape.

The valve seat portion 31 a is connected to the portion 31 h 2 of another shape (i.e., a round columnar shape) of the throat portion 31 b. The valve seat portion 31 a may also be connected to a bottom surface of the truncated cone portion 31 b 1 (not via the portion 31 b 2 of another shape). In other words, the throat portion 31 b may also be connected to the valve seat portion 31 a such that at least a portion of a boundary line between the throat portion 31 b and the valve seat portion 31 a is on a bottom surface of the truncated cone shape of the throat portion 31 b.

When the air-fuel mixture passes through the intake port 31 and is introduced into the combustion chamber 25, the air-fuel mixture passes through the passage portion 31 c, the throat portion 31 b, and the valve seat portion 31 a in this order (see arrow IN in FIG. 2). In this way, the intake port 31 forms a portion of the flow path through which the air-fuel mixture introduced from outside of the combustion chamber 25 into the combustion chamber 25 passes.

Hereinafter, regarding the intake port 31, the outer peripheral surface of the flow path itself through which the air-fuel mixture passes and the inner peripheral surface of the member that defines this flow path may also be referred to as a “peripheral surface of the intake port 31”. Similarly, regarding the valve seat portion 31 a, the throat portion 31 b, and the passage portion 31 c, hereinafter, the outer peripheral surface of the flow path itself through which the air-fuel mixture passes and the inner peripheral surface of the members that define this flow path may also be referred to as a “peripheral surface of the valve seat portion 31 a”, a “peripheral surface of the throat portion 31 b”, and a “peripheral surface of the passage portion 31 c”.

Referring back to FIG. 2 again, the exhaust port 35 has the same structure as the intake port 31 (i.e., has the throat portion, a valve seat portion, and a passage portion). Here, a detailed description of the structure of the exhaust port 35 will be omitted. When exhaust gas passes through the exhaust port 35 and is discharged from the combustion chamber 25, the exhaust gas passes through the valve seat portion, the throat portion, and the passage portion in this order (see arrow EX in FIG. 2). In this embodiment, the exhaust port 35 represents a flow path itself through which exhaust gas passes that is between the combustion chamber 25 and an exhaust manifold 51 that will be described later, or a member that defines this flow path.

The passage through which the air-fuel mixture passes is closed off by the intake valve 32 contacting the valve seat portion 31 a of the intake port 31 structured as described above, and the passage through which the air-fuel mixture passes is Opened by the intake valve 32 coming away from the valve seat portion 31 a. That is, the intake port 31 opens and closes according to the intake valve 32, and similarly, the exhaust port 35 opens and closes according to the exhaust valve 36.

Referring back to FIG. 1 again, the intake system 40 includes an intake manifold 41 that is communicated to each cylinder via the intake port 31 described above, an intake pipe 42 that is connected to a converging portion upstream of the intake manifold 41, an air cleaner 43 provided on an end portion of the intake pipe 42, a throttle valve (i.e., an intake throttle valve) 44 capable of changing the opening area (i.e., the opening sectional area) of the intake pipe 42, and a throttle valve actuator 44 a that rotatably drives the throttle valve 44 according to a command signal. The intake port 31, the intake manifold 41, and the intake pipe 42 together form an intake passage.

The exhaust system 50 includes an exhaust manifold 51 that is communicated with each of the cylinders via the exhaust port 35 described above, an exhaust duct 52 that is connected to a converging portion downstream of the exhaust manifold 51, and an exhaust gas control catalyst 53 provided in the exhaust duct 52. The exhaust port 35, the exhaust manifold 51, and the exhaust duct 52 together form an exhaust passage.

Referring to FIG. 1 again, the accelerator pedal 61 for inputting an acceleration request and the required torque and the like to the internal combustion engine 10 is provided outside of the internal combustion engine 10. The accelerator pedal 61 is operated by an operator of a vehicle provided with the internal combustion engine 10.

The internal combustion engine 10 is provided with various sensors, such as an intake air amount sensor 71, a throttle valve opening amount sensor 72, a crank position sensor 73, a coolant temperature sensor 74, air-fuel ratio sensors 75 and 76, and an accelerator operation amount sensor 77.

Of these sensors, the crank position sensor 73 is provided near the crankshaft 24. The crank position sensor 73 is configured to output a signal having a narrow pulse width every time the crankshaft 24 rotates 10°, and output a signal having a wide pulse width every time the crankshaft 24 rotates 360°. The rotation speed per unit time of the crankshaft 24 (hereinafter, also simply referred to as “engine speed NE”) can be obtained based on these signals.

Furthermore, the internal combustion engine 10 includes the ECU 80. The ECU 80 includes a CPU 81, ROM 82 in which programs to be executed by the CPU 81, as well as constants and tables (maps), have been stored in advance, RAM 83 in which data is temporarily stored as necessary by the CPU 81, back-up RAM 84 that stores data when a power supply is on and retains the stored data while the power supply is off, and an interface 85 that includes an AD converter. The CPU 81, the ROM 82, the RAM 83, the back-up RAM 84, and the interface 85 are all connected together by a bus.

The interface 85 is connected to the various sensors and is configured to transmit the signals output from these sensors to the CPU 81. Furthermore, the interface 85 is connected to the injector 34, the igniter 39, and the throttle valve actuator 44 a and the like, and is configured to send command signals to these according to a command from the CPU 81.

Relationship Between Variation and Flow of Air-Fuel Mixture

As described above, there may be variation among the members that make up the intake port 31. Next, the relationship between variation among the members that make up the intake port 31 and the flow of air-fuel mixture that passes through the intake port 31 will be described.

First, before describing this relationship with respect to the intake port 31 according to the first embodiment, this relationship with respect to an intake port according to related art will be described. FIG. 4 is a schematic diagram of the manner in which gas passes through an intake port 91 according to related art. As shown in FIG. 4, the intake port 91 according to the related art differs from the intake port 31 according to the first embodiment of the invention in that the throat portion has a portion in the shape of an ellipsoid (in other words, in a semispherical shape).

Reference character A in FIG. 4 denotes a peripheral surface of a passage portion when there is no variation among the members that make up the intake port 91. In this case, the size of the angle defined by the peripheral surface A of the passage portion and a tangential plane (the alternate long and short dash line in the drawing) of the throat portion, in a position where the peripheral surface A of the passage portion is connected to the throat portion is angle α.

When the air-fuel mixture that flows close to the peripheral surface A of the passage portion passes through the intake port 91, it is assumed that the air-fuel mixture flows along the peripheral surface A of the passage portion and the peripheral surface of the throat portion, as shown by the solid arrow in the drawing.

On the other hand, reference character B in FIG. 4 denotes a peripheral surface B of the passage portion when there is variation among the members that make up the intake port 91. More specifically, in this case, there is variation such that the position where the peripheral surface of the passage portion is connected to the throat portion approaches the center (i.e., the axis) of the passage portion (i.e., shifts upward in the drawing) by δ. Hereinafter, this variation may also be referred to as “variation δ”. The slope of the tangential plane of the ellipsoid typically differs depending on the position where the throat portion is connected to the passage portion, so in this case, the size of the angle defined by the peripheral surface B of the passage portion and the tangential plane (i.e., the alternate long and short dash line in the drawing) of the throat portion is angle β that is different from angle α. In this embodiment, angle β is smaller than angle α.

When the air-fuel mixture that flows close to the peripheral surface B of the passage portion passes through the intake port 91, the air-fuel mixture may not flow along the peripheral surface B of the passage portion and the peripheral surface of the throat portion because angle β is smaller than angle α. For example, as shown by the broken arrow in the drawing, the air-fuel mixture may flow in a different direction than the solid arrow described above due to the air-fuel mixture separating from these peripheral surfaces at the position where the peripheral surface B of the passage portion is connected to the throat portion.

That is, the flow direction of the air-fuel mixture that passes through the intake port 91 when there is no variation among the members that make up the intake port 91 may be different from the flow direction of that air-fuel mixture when there is variation among these members. If the flow direction of the air-fuel mixture that passes through the intake port 91 changes, the intended characteristics of the intake port (such as the tumble ratio that will be described later with reference to FIG. 13, for example) may be unable to be obtained.

In contrast, FIG. 5 is a schematic diagram of the manner in which gas passes through the intake port 31 according to the first embodiment of the invention. As described above, reference character A in FIG. 5 denotes a peripheral surface of the passage portion when there is no variation among the members that make up the intake port 31, and reference character B in FIG. 5 denotes a peripheral surface of the passage portion when there is the same variation δ as described above among the members.

The slope of the side surface of the truncated cone typically will not change as long as the position where the passage portion is connected to the throat portion changes on the same line. Therefore, the size of the angle defined by the passage portion, the peripheral surface A, and the side surface of the throat portion, and the size of the angle defined by the passage portion, the peripheral surface B, and the side surface of the throat portion are the same angle γ. Therefore, the air-fuel mixture that flows close to the peripheral surface A of the passage portion (i.e., the solid arrow in the drawing) and the air-fuel mixture that flows close to the peripheral surface B of the passage portion (i.e., the broken arrow in the drawing) flow in essentially the same direction.

That is, the flow direction of the air-fuel mixture that passes through the intake port 31 when there is no variation among the members that make up the intake port 31 is essentially the same as the flow direction of that air-fuel mixture when there is variation among those members.

In this way, even if there is variation among the members that make up the intake port 31, the intake port 31 according to the first embodiment of the invention is able to inhibit a change in the flow direction of the air-fuel mixture that passes through the intake port due to this variation, compared with the intake port 91 according to the related art. As a result, with the intake port 31, the intended characteristics of the port are able to be obtained to the greatest extent possible.

Second Embodiment

Next, a port according to a second embodiment of the invention will be described.

Outline of the Port

The port according to the second embodiment of the invention differs from the port according to the first embodiment described above only in that the valve seat portion has a specific mode. Therefore, the port according to the second embodiment will be described in detail focusing on this difference. In FIGS. 6 and 7 described below, members that are the same as those that make up the port according to the first embodiment will be denoted by the same reference characters as those denoting the members in the first embodiment.

FIG. 6 is an enlarged perspective view schematically showing the port 31 that is the port according to the second embodiment. Just like the intake port according to the first embodiment, the valve seat portion 31 a is connected to a combustion chamber side end portion of the throat portion 31 b so as to communicate the throat portion 31 b with the inside of the combustion chamber 25. Moreover, the valve seat portion 31 a has a plurality (four in this embodiment) of annular surfaces, as shown by the hatched portion. One of these four annular surfaces is connected to another of the surfaces that is adjacent to this one surface. Each of the four annular surfaces is a ring formed by a closed band having a flat surface.

FIG. 7 is a view schematically showing a cross section of the combustion chamber 25, the intake port 31, and the exhaust port 35 when a region including the combustion chamber 25, the intake port 31, and the exhaust port 35 has been cut along a plane parallel to the axis of the combustion chamber 25. Moreover, in FIG. 7, an enlarged view of the area (i.e., portion C in the drawing) near the boundary between the combustion chamber 25 and the valve seat portion 31 a of the intake port 31 is also shown.

As shown in the enlarged view of portion C, the size of an angle defined by a first surface 31 a 1 and a second surface 31 a 2 adjacent to the first surface 31 a 1, from among the four annular surfaces, is angle θ. Further, the size of an angle defined by the second surface 31 a 2 and a third surface 31 a 3 adjacent to the second surface 31 a 2 is also Angle θ. In addition, the size of an angle defined by the third surface 31 a 3 and a fourth surface 31 a 4 adjacent to the third surface 31 a 3 is also angle θ. That is, each angle defined by two adjacent surfaces among the four annular surfaces is the same (i.e., angle θ).

The intake port 31 according to the second embodiment having the structure described above may be applied to an internal combustion engine having a structure similar to that of the internal combustion engine 10 described above (see FIG. 1).

Flow of Air-Fuel Mixture that Passes Through the Valve Seat Portion

When the air-fuel mixture passes through the valve seat portion 31 a, the flow direction of the air-fuel mixture that flows close to the peripheral surface of the valve seat portion 31 a will change by the same angle θ each time the air-fuel mixture passes by a connecting position of the four annular surfaces. Therefore, it is unlikely that the air-fuel mixture will separate from the valve seat portion 31 a, compared with a valve portion in which these angles are not the same.

Therefore, the intake port 31 is more appropriately able to control the flow of gas in the combustion chamber 25.

The angle defined by two adjacent surfaces from among the four annular surfaces is not particularly limited as long as it is an angle at which separating can be inhibited, taking into account the characteristics of the air-fuel mixture and the like. For example, the angle may be 15°.

Third Embodiment

Next, a port according to a third embodiment of the invention will be described.

Outline of the Port

The port according to the third embodiment of the invention differs from the port according to the first embodiment described above only in that the valve seat portion has a specific mode. Therefore, the port according to the third embodiment will be described in detail focusing on this difference. In FIG. 8 described below, members that are the same as those that make up the port according to the first embodiment will be denoted by the same reference characters as those denoting the members in the first embodiment.

FIG. 8 is a view schematically showing a cross section of the combustion chamber 25, the intake port 31, and the exhaust port 35 when a region including the combustion chamber 25, the intake port 31, and the exhaust port 35 has been cut along a plane parallel to the axis of the combustion chamber 25. Moreover, in FIG. 8, an enlarged view of the area (i.e., portion D in the drawing) near the boundary between the combustion chamber 25 and the valve seat portion 31 a of the intake port 31 is also shown.

Just like the intake port according to the second embodiment described above, the intake port 31 has a plurality (four in this embodiment) of annular surfaces that are connected together. As shown in the enlarged view of portion D, the size of the width of the first surface 31 a 1 among the four annular surfaces is width w. Furthermore, the size of the width of the second surface 31 a 2 is also width w. In addition, the size of the width of the third surface 31 a 3 is also width w, and the size of the width of the fourth surface 31 a 4 is also width w. That is, the width of the each of the four annular surfaces is the same (i.e., width w).

The intake port 31 according to the third embodiment having the structure described above may be applied to an internal combustion engine having a structure similar to that of the internal combustion engine 10 described above (see FIG. 1).

Flow of Air-Fuel Mixture that Passes Through the Valve Seat Portion

When the air-fuel mixture passes through the valve seat portion 31 a, the flow direction of the air-fuel mixture that flows close to the peripheral surface of the valve seat portion 31 a will change with each advance of the same distance (i.e., width w). Therefore, it is unlikely that the air-fuel mixture will separate from the valve seat portion 31 a, compared with a valve portion in which these widths are not the same.

Therefore, the intake port 31 is more appropriately able to control the flow of gas in the combustion chamber 25.

Fourth Embodiment

Next, a port according to a fourth embodiment of the invention will be described.

Outline of the Port

The port according to the fourth embodiment of the invention differs from the port according to the first embodiment described above only in that the throat portion and the passage portion are connected in a specific way. Therefore, the port according to the fourth embodiment will be described in detail focusing on this difference. In FIGS. 9 and 13 described below, members that are the same as those that make up the port according to the first embodiment will be denoted by the same reference characters as those denoting the members in the first embodiment.

FIG. 9 is an enlarged perspective view schematically showing a port 31 that is the port according to the fourth embodiment. Just like the intake port according to the first embodiment, the passage portion 31 c is connected to the intake side end portion of the throat portion 31 b so as to communicate the throat portion 31 b with the outside of the combustion chamber 25.

More specifically, the throat portion 31 b and the passage portion 31 c are connected together such that an axis E of the throat portion 31 b and an axis F of the passage portion 31 c are in the same plane.

Further, the throat portion 31 b and the passage portion 31 c are connected together such that at least a portion of an extension line 31 bext of a generating line 31 bgen of the truncated cone shape 31 b 1 of the throat portion 31 b (hereinafter this extension line 31 bext may also be referred to as a “generating line extension line 31 bext”) is included in a peripheral surface 31 cper that includes a boundary line 31 bcbo between the passage portion 31 c and the throat portion 31 b, and that is a peripheral surface of the passage portion 31 c (hereinafter this peripheral surface may also be referred to as a “peripheral surface close to the connecting position”).

In other words, the throat portion 31 b and the passage portion 31 c are connected together such that an angle defined by the side surface of the truncated cone shape 31 b 1 of the throat portion 31 b and the peripheral surface 31 cper close to the connecting position is zero (or 180°) on the generating line extension line 31 bext.

The intake port 31 according to the fourth embodiment having the structure described above may be applied to an internal combustion engine having a structure similar to that of the internal combustion engine 10 described above (see FIG. 1).

Flow of Gas Inside the Combustion Chamber

Next, the flow in the combustion chamber 25 of the air-fuel mixture that has passed through the intake port 31 will be described.

First, before the flow in the intake port 31 according to the fourth embodiment is described, the flow inside the combustion chamber 25 of the air-fuel mixture that has passed through an input port of related art will be described. FIG. 10 is a view schematically showing a cross section of the combustion chamber 25, an intake port 101, and an exhaust port 102 when a region including the combustion chamber 25, the intake port 101, and the exhaust port 102 has been cut along a plane parallel to the axis of the combustion chamber 25, in an internal combustion engine 10 to which the intake port 101 and the exhaust port 102 according to related art have been applied. Similar to FIG. 2, members that are not absolutely necessary to describe the structure of the ports according to this embodiment are not shown in FIG. 10.

The intake port 101 of the related art differs from the intake port 31 according to the fourth embodiment of the invention only in that a throat portion 101 b has at least a portion of an ellipsoid shape (in other words, has a semispherical shape). That is, a valve seat portion 101 a and a passage portion 101 c of the related art have the same shapes as the valve seat portion 31 a and the passage portion 31 c, respectively, of the intake port 31 according to the fourth embodiment of the invention, and are connected to the throat portion 101 b, just as with the intake port 31.

FIG. 11 is a schematic diagram of an example of the flow inside the combustion chamber 25 of air-fuel mixture that has flowed through the intake port 101 of the related art when the intake valve 32 is open and the exhaust valve 36 is closed (i.e., during an intake stroke).

As shown in FIG. 11, of the air-fuel mixture introduced into the combustion chamber 25, an air-fuel mixture INdir that flows toward a side surface 25 a of the combustion chamber 25 that is farthest away from the intake port 101 (hereinafter, this side surface 25 a will be referred to as an “exhaust side peripheral surface 25 a”) passes through the intake port 101 by flowing along a peripheral surface 101 bus near the exhaust side peripheral surface 25 a of the peripheral surface of the throat portion (hereinafter, this peripheral surface 101 bus may also be referred to as an “upper peripheral surface 101 bus”). The air-fuel mixture INdir is denoted by the solid line in the drawing.

The throat portion in the related art has a semispherical shape, so when the air-fuel mixture INdir passes through the throat portion, the flow direction of the air-fuel mixture INdir changes so that it is along the upper peripheral surface 101 bus of the throat portion (i.e., changes to a direction toward the intake valve 32 in the drawing; in other words, changes to a direction away from a peripheral surface 101 aus of the valve seat portion). As a result, as shown in FIG. 11, the air-fuel mixture INdir may separate from the peripheral surface of the intake port 101 near the position where the upper peripheral surface 101 bus of the throat portion is connected to the peripheral surface 101 aus of the valve seat portion.

On the other hand, of the air-fuel mixture introduced into the combustion chamber 25, an air-fuel mixture INinv that flows toward a peripheral surface 25 b of the combustion chamber 25 that is closest to the intake port 101 (hereinafter, this peripheral surface 25 b will be referred to as an “intake side peripheral surface 25 b”) passes through the intake port 101 by flowing along a peripheral surface 101 cls of the passage portion, and a peripheral surface 101 bls that is close to the intake side peripheral surface 25 b, from among the peripheral surfaces of the throat portion (hereinafter, this peripheral surface 101 bls may also be referred to as a “lower peripheral surface 101 bls”). The air-fuel mixture INinv is denoted by the broken line in the drawing.

This air-fuel mixture INdir is able to be introduced into the combustion chamber 25 without separating from the peripheral surface of the intake port 101, as shown in FIG. 11, as long as the connecting angle between the lower peripheral surface 101 bls of the throat portion and the peripheral surface 101 cls of the passage portion, and the connecting angle between the lower peripheral surface 101 bls of the throat portion and a peripheral surface 101 als of the valve seat portion, are appropriate.

In this way, with the intake port 101 of the related art, the air-fuel mixture INdir that flows close to the upper peripheral surface 101 bus of the throat portion may separate from the peripheral surface of the intake port 101. In this case, the air-fuel mixture INdir is not suitably introduced into the combustion chamber 25, so the flow of the air-fuel mixture inside of the combustion chamber 25 is unable to be appropriately controlled. For example, the tumble ratio and the flowrate of the air-fuel mixture introduced into the combustion chamber 25 will not be sufficiently increased (see also FIG. 13 that will be described later).

One conceivable way to prevent the air-fuel mixture INdir from separating from the intake port 101 is to incline the intake port 101 to a degree at which the air-fuel mixture INdir will not separate from the side surface of the intake port 101 near the position where the upper peripheral surface 101 bus of the throat portion is connected to the peripheral surface 101 aus of the valve seat portion. For example, as shown in FIG. 12, the intake port 101 may be inclined such that an axis of the intake port 101 matches an axis H that is inclined by an angle ε with respect to an axis G of the intake port 101 in FIG. 11.

If the intake port 101 is inclined as described above, the air-fuel mixture INdir that flows toward the exhaust side peripheral surface 25 a will flow in a direction closer to the peripheral surface 101 aus of the valve seat portion than that shown in FIG. 11. Therefore, the air-fuel mixture INdir is able to be introduced into the combustion chamber 25 without separating from the peripheral surface of the intake port 101.

If the intake port 101 is inclined as described above, the connecting angle between the lower peripheral surface 101 bls of the throat portion and the peripheral surface 101 cls of the passage portion, or the connecting angle between the lower peripheral surface 101 bls of the throat portion and the peripheral surface 101 als of the valve seat portion, will change. Therefore, the air-fuel mixture INinv may separate from the peripheral surface of the intake port 101 close to the position where the lower peripheral surface 101 bls of the throat portion is connected to the peripheral surface 101 als of the valve seat portion, for example.

In this way, if the intake port 101 of the related art is inclined, even though the air-fuel mixture INdir that flows close to the upper peripheral surface 101 bus of the throat portion is able to be prevented from separating from the intake port 101, the air-fuel mixture INinv that flows close to the lower peripheral surface 101 bls of the throat portion may separate from the peripheral surface of the intake port 101. In this case, the flow of the air-fuel mixture inside of the combustion chamber 25 is unable to be appropriately controlled, just as described above.

In contrast, FIG. 13 is a schematic diagram of an example of flow inside of the combustion chamber 25 of the air-fuel mixture that has passed through the intake port 31 according to the fourth embodiment of the invention. Just as described above, members that are not absolutely necessary to describe the structure of the port according to this embodiment are not shown in FIG. 13.

As shown in FIG. 13, in the intake port 31 of this embodiment, neither the air-fuel mixture INdir nor the air-Rid mixture INinv separate from the intake port 31, and the air-fuel mixture INdir creates a rotating flow (i.e., tumbling flow) inside of the combustion chamber 25.

More specifically, first the air-fuel mixture INdir that flows toward the exhaust side peripheral surface 25 a passes through the intake port 31 by flowing along an upper peripheral surface 31 bus of the intake port 31. In the intake port 31, the throat portion 31 b and the passage portion 31 c are connected together such that the axis E of the throat portion 31 b and the axis F of the passage portion 31 c are in the same plane, as described above. Therefore, when the air-fuel mixture passes through the throat portion 31 b, the flow direction of the air-fuel mixture that flows along the peripheral surface of the throat portion 31 b is parallel to the generating line 31 bgen of the truncated cone shape 31 b 1 of the throat portion 31 b.

Therefore, the air-fuel mixture INdir differs from that of the related art (i.e., the flow direction of the air-fuel mixture when it passes through the throat portion 101 b changes; see FIG. 11), and is able to pass through the intake port 31 without separating from the intake port 31 near the position where the upper peripheral surface 31 bus of the throat portion is connected to a peripheral surface 31 aus of the valve seat portion.

Moreover, with the intake port 31, the throat portion 31 b is connected to the passage portion 31 c such that at least a portion of the generating line extension line 31 bext of the truncated cane shape 31 b 1 of the throat portion 31 b is included in the peripheral surface 31 cper that is close to the connecting position of the passage portion 31 c (see FIG. 9). Therefore, when the air-fuel mixture INdir passes through the passage portion and the throat portion, the flow direction of the air-fuel mixture INdir does not change.

Accordingly, when the air-fuel mixture INdir passes through the passage portion and the throat portion, the flow direction of the air-fuel mixture INdir does not change, so compared with the related art described above, the energy loss of the air-fuel mixture INdir when the air-fuel mixture INdir passes through the intake port 31 is able to be reduced.

In this embodiment, the direction of the generating line extension line 31 bext of the throat portion 31 b (see FIG. 9; this direction corresponds to the direction of axis F of the intake port 31 in FIG. 13) is adjusted so that the angular velocity ω of the rotating flow (i.e., the tumble) created inside of the combustion chamber 25 by the air-fuel mixture INdir is as large as possible. For example, the direction of the generating line extension line 31 bext of the throat portion 31 b is adjusted so that the flowrate of the air-fuel mixture INdir when the air-fuel mixture INdir reaches the exhaust side peripheral surface 25 a of the combustion chamber 25 is as large as possible (simply put, so that it heads straight toward the exhaust side peripheral surface 25 a).

More specifically, the air-fuel mixture INdir that has been introduced into the combustion chamber 25 flows along the exhaust valve 36, the exhaust side peripheral surface 25 a, the piston 22, and the intake side peripheral surface 25 b, in this order. As a result, the air-fuel mixture INdir creates a rotating flow (so-called tumble) that rotates around an axis perpendicular to the axis of the combustion chamber 25, in the combustion chamber 25.

Here, typically a ratio (ω/NE) of the angular velocity ω of the rotating flow (i.e., tumble) inside of the combustion chamber 25 with respect to the engine speed NE of the internal combustion engine 10 will be referred to as the tumble ratio. As can be understood from this description, the value of the tumble ratio increases as the angular velocity ω of the tumble with respect to the unit value of the engine speed NE increases (i.e., as stronger tumble is created inside the combustion chamber 25). One method that may be used to calculate the tumble ratio is a method that calculates the tumble ratio based on, for example, the results of a measurement taken in advance using a test engine having a structure similar to that of the internal combustion engine 10, or the results of a simulation that estimates the flow of air-fuel mixture inside the combustion chamber 25.

As described above, in this embodiment, the angular velocity ω of the rotating flow (i.e., tumble) can be increased by adjusting the direction of the generating line extension line 31 bext of the throat portion 31 b (in other words, the flow direction of the air-fuel mixture introduced into the combustion chamber 25). Therefore, the internal combustion engine 10 that uses the intake port 31 according to this embodiment is able to increase the tumble ratio more than the internal combustion engine 10 that uses the intake port 101 according to the related art.

When the tumble ratio is increased, flame propagation when the air-fuel mixture is combusted progresses more smoothly, so the air-fuel mixture is able to be combusted more efficiently. As a result, fuel efficiency is able to be improved, for example.

Furthermore, the air-fuel mixture INinv that flows toward the intake side peripheral surface 25 b passes through the intake port 31 by flowing along a peripheral surface 31 cls of the passage portion, a lower peripheral portion 31 bls of the throat portion, and a peripheral portion 31 als of the valve seat portion. With the intake port 31 of this embodiment, the air-fuel mixture INdir that flows close to the upper peripheral surface 31 bus of the throat portion can be prevented from separating from the intake port 31 without inclining the intake port as in the related art (FIG. 12), as described above. Therefore, the connecting angle between the lower peripheral surface 31 bls of the throat portion and the peripheral surface 31 cls of the passage portion, and the connecting angle between the lower peripheral surface 31 bls of the throat portion and the peripheral surface 31 als of the valve seat portion can be set to appropriate angles at which the air-fuel mixture INdir will not separate. Accordingly, the air-fuel mixture INdir can be introduced into the combustion chamber 25 without separating from the peripheral surface of the intake port 31.

As described above, in this embodiment, the air-fuel mixture (both the air-fuel mixture INinv and the air-fuel mixture INdir) that passes through the intake port 31 can be prevented from separating from the intake port 31. Therefore, the internal combustion engine 10 in which the intake port 31 of this embodiment is employed is able to increase the flowrate of the air-fuel mixture that is introduced into the combustion chamber 25 more than the internal combustion engine 10 in which the intake port 101 of the related art is employed.

Increasing the flowrate of the air-fuel mixture introduced into the combustion chamber 25 enables the energy generated when the air-fuel mixture is combusted to be increased, so the output of the internal combustion engine 10 is able to be increased.

In this embodiment, the tumble ratio is able to be increased by adjusting the flow direction of the air-fuel mixture that is introduced into the combustion chamber 25, so the flowrate of the air-fuel mixture does not need to be increased (e.g., the opening diameter of the port does not need to be made smaller) in order to increase the tumble ratio. Therefore, an increase in the temperature of the air-fuel mixture due to an increase in the flowrate of the air-fuel mixture, as well as an increase in knocking caused by this increase in temperature of the air-fuel mixture, can be inhibited. Also, a decrease in the flowrate of the air-fuel mixture due to the opening diameter of the port being smaller, as well as a decrease in the output of the internal combustion engine 10 due to this decrease in the flowrate of the air-fuel mixture, can also be inhibited.

As described above, the intake port 31 according to the fourth embodiment is able to appropriately control the flow of the air-fuel mixture inside of the combustion chamber 25. As a result, the intended characteristics of the port can be more reliably obtained.

As can be understood from the description above, combining the intake port 31 according to the first embodiment (i.e., suppressing the effects from variation), the intake port 31 according to the second or third embodiment described above (i.e., the shape of the valve seat portion), and the intake port 31 according to the fourth embodiment (i.e., the way in which the throat portion and the passage portion are connected) enables the flowrate of the air-fuel mixture that is introduced into the combustion chamber 25 and the tumble ratio to be further improved, while suppressing the effects from variation among the members that make up the intake port 31. For example, as shown in the graph showing a simple view of the relationship between the flowrate and the tumble ratio in FIG. 14, the port of the invention is able to increase both the tumble ratio and the flowrate more than the port of the related art (see FIG. 10), while reducing the effects that variation has on the tumble ratio and the flowrate more than the port of the related art (see FIG. 10).

Summary of the Embodiments

As described above, the ports according to the embodiments (i.e., the first through the fourth embodiments) of the invention are provided with the throat portion 31 b that has at least a portion of a truncated cone shape (the truncated cone portion 31 b 1 in FIG. 3), the valve seat portion 31 a that is connected to one end portion (i.e., the combustion chamber side end portion) of the throat portion 31 b so as to communicate the throat portion 31 b with the inside of the combustion chamber 25, and the passage portion 31 c that is connected to the other end portion (i.e., the intake side end portion) of the throat portion 31 b so as to communicate the throat portion 31 b with the outside of the combustion chamber 25 (see FIGS. 2 and 3, for example).

In the ports according to the embodiments, the valve seat portion 31 a has three or more annular surfaces (such as four annular surfaces; see FIG. 6) in which the angle defined by any two adjacent surfaces, from among these annular surfaces, is the same (angle θ in FIG. 7).

Moreover, in the ports according to the embodiments, the valve seat portion 31 a has a plurality of annular surfaces (three or more annular surfaces; for example, four annular surfaces) in which the width of each of the plurality of annular surfaces is the same (width w in FIG. 8).

In the ports according to the embodiments, the valve seat portion 31 a has four annular surfaces (see FIG. 6).

Furthermore, the ports according to the embodiments are such that the throat portion 31 b is connected to the passage portion 31 c such that the flow direction of gas that flows along the peripheral surface of the throat portion 31 b is parallel to the generating line 31 bgen of the truncated cone shape 31 b 1 of the throat portion 31 b when gas passes through the throat portion 31 b.

That is, for example, the port of the invention is such that the throat portion 31 b is connected to the passage portion 31 c such that the axis E of the throat portion 31 b and the axis F of the passage portion 31 c are in the same plane.

Moreover, in the ports according to the embodiments, the throat portion 31 b is connected to the passage portion 31 c such that at least a portion of the generating line extension line 31 bext that is an extension line of the generating line 31 bgen of the truncated cone shape 31 b 1 of the throat portion 31 b is included in the peripheral surface 31 cper that includes the boundary line 31 bcbo between the passage portion 31 c and the throat portion 31 b, and that is a peripheral surface of the passage portion 31 c.

Other Modes

The invention is not limited to the embodiments described above. That is, various modified examples may also be employed within the scope of the invention.

For example, the ports according to the embodiments described above are applied to the spark-ignition internal combustion engine 10. However, the port of the invention may also be applied to an engine other than a spark-ignition engine (such as a diesel engine).

Furthermore, in the embodiments described above, the port is applied to the intake port 31. However, the port of the invention may also be applied to an exhaust port.

In addition, in the embodiments described above, the valve seat portion 31 a of the intake port 31 has four annular surfaces. However, the number of annular surfaces of the valve seat portion is not particularly limited as long as it is set to a suitable value that takes into account the ability to block off gas in the port and the cost for forming the valve seat portion and the like.

Moreover, in the embodiments described above, the passage portion 31 c has a round columnar shape. However, the passage portion 31 c may have a square columnar shape or an elliptical columnar shape or the like.

Further, in the embodiments described above, the throat portion 31 b has the truncated cone-shaped portion 31 b 1. However, the throat portion may be configured to have a complete truncated cone shape.

Also, in the embodiments described above, the plurality of annular surfaces (31 a 1 to 31 a 4) that make up the valve seat portion 31 a are configured to be rings formed by closed bands having flat surfaces. However, the plurality of annular surfaces may also be rings formed by closed bands having curved surfaces. Also, if rings formed by closed bands having curved surfaces are used as the annular surfaces, the curvature radius of the curved surfaces may be set such that another curved surface is formed by a portion or all of the plurality of annular surfaces. 

1. A port that communicates an inside of a combustion chamber of an internal combustion engine with an outside of the combustion chamber, comprising: a throat portion that has at least a portion of a truncated cone shape; a valve seat portion that is connected to one end portion of the throat portion to communicate the throat portion with the inside of the combustion chamber; and a passage portion that is connected to the other end portion of the throat portion to communicate the throat portion with the outside of the combustion chamber.
 2. The port according to claim 1, wherein the throat portion is formed by a portion formed in a truncated cone shape and a portion formed in a round columnar shape.
 3. The port according to claim 1, wherein the throat portion is formed by only a portion formed in a truncated cone shape.
 4. The port according to claim 1, wherein the valve seat portion has three or more annular surfaces in which an angle defined by any two adjacent surfaces, from among the three or more annular surfaces, is the same.
 5. The port according to claim 4, wherein a width of each of the three or more annular surfaces is the same.
 6. The port according to claim 1, wherein the valve seat portion has a plurality of annular surfaces in which a width of each of the plurality of annular surfaces is the same.
 7. The port according to claim 1, wherein the valve seat portion has four annular surfaces.
 8. The port according to claim 1, wherein the throat portion is connected to the passage portion such that a flow direction of gas that flows along a peripheral surface of the throat portion is parallel to a generating line of the truncated cone shape of the throat portion when gas passes through the throat portion.
 9. The port according to claim 8, wherein the throat portion is connected to the passage portion such that an axis of the throat portion and an axis of the passage portion are in the same plane.
 10. The port according to claim 1, wherein the throat portion is connected to the passage portion such that at least a portion of an extension line of a generating line of the truncated cone shape of the throat portion is included in a peripheral surface that includes a boundary line between the passage portion and the throat portion, and that is a peripheral surface of the passage portion. 